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Conservative Management of Tooth Discoloration

Douglas A. Terry, DDS

Contemporary
emphasis on personal health and appearance is the catalyst for the demand of products
and procedures that improve the appearance of teeth.1 The influence
of the media and public desire for cosmetic enhancement has stimulated short-term
attractive smiles at the expense of long-term dental health.2
Preserving and stabilizing the hard tissues requires more than a rudimentary
understanding of new materials and techniques. It also requires the clinician
to be aware of less destructive alternative restorative procedures to correct
or improve the appearance of aesthetic deficiencies while incorporating a
restorative philosophy of prevention, preservation, and perpetuation of
longevity into his or her diagnosis and treatment planning.3

The
clinician begins to correct restorative and aesthetic challenges by selecting a
progressive treatment concept that begins with the most conservative
restorative option and progresses to more invasive procedures as required.2
Additionally, the method of informing patients to ensure proper decision making
should be directed toward the long-term biomechanical risks associated with
more invasive procedures. Modern restorative principles encompass a myriad of
disciplines and conservative approaches that are available for numerous
procedures. This discussion on the aesthetic correction of tooth discoloration
will consider alternative conservative procedures.

Enamel Surface Discolorations

Correction
of discolored teeth has been described in the literature since the 20th century.4
Enamel discoloration can result from extrinsic and intrinsic staining and from
abnormal mineralization. Extrinsic stains can be the result of accumulation and
adherence of foreign particles on the tooth surface (eg, tobacco, wine).
Intrinsic stains are caused by coloration agents entering the enamel and dentin
or structural alterations by genetic or environmental stimuli (eg,
dentinogenesis imperfecta, amelogenesis imperfecta, tetracycline
discoloration).1 Other forms of intrinsic staining are enamel
dysmineralization5 and enamel decalcification.1 Enamel
dysmineralization refers to enamel coloration defects that occur from a
disturbance in the formation of the inorganic component of enamel during
amelogenesis.5 These enamel surface defects can exhibit white
opacities, brown, yellow, or orange opacious spots and streaks, or multicolored
superficial defects.5,6 Enamel decalcification lesions occur when
dental plaque persists on the enamel and the resulting organic acids etch the
mineral content from the enamel surface. These lesions exhibit white
colorations and, if left undisturbed, can result in caries (eg, brown
colorations); these are usually associated with the area around resin-bonded
orthodontic brackets and the cervical margins of all teeth.1

The
successful elimination of discoloration depends primarily on the depth the
lesion has penetrated the tooth’s surface.5 Although prevention is preferred,
the precise etiology of the lesion often cannot be ascertained at the
appropriate time, and for some intrinsic discolorations,
the cause is unknown.5 Restorative treatments of discoloration have
included conservative to more invasive procedures, including chemical
treatments (ie, bleaching), enamel microabrasion, direct composite resin,
composite and porcelain veneers, and porcelain crowns. Treatment considerations
should begin with the most conservative procedures and progress as needed to
more invasive alternatives depending upon the depth of the lesion.

Conservative Color Correction

Conservative
treatment considerations for correcting discoloration include dental bleaching
and enamel microabrasion.1,5,7 These procedures are considered to be
less destructive alternatives to the mechanical removal of discolored enamel
and its subsequent replacement with a restorative material.8

The
difference between dental bleaching and enamel microabrasion is not only the
chemical agent used for improving tooth color, but for the results of the
process. Bleaching is a chemical process of applying oxidizing agents on the
tooth surface that penetrate the enamel and dentin and result in color alterations,
but not in enamel reduction. Enamel microabrasion is a chemical and micromechanical
method of reducing a microscopic layer of the enamel surface while eliminating
superficial enamel discolorations. Bleaching can therefore be used for
transitory color correction by altering enamel and dentinal discolorations (ie,
intrinsic tetracycline staining), while enamel microabrasion can provide a
permanent elimination for some superficial enamel discolorations.7

A
combination approach of using enamel microabrasion followed by patient-administered
home bleaching applications can unify color correction, especially with
discolorations such as decalcification, fluorosis, and fluorosis-like defects.9

Enamel Microabrasion

The
microabrasion technique incorporates the use of an acid with abrasive particles
to eliminate discolorations (Table). The treatment time for this procedure can
be reduced by using rotary cutting devices such as fine diamond burs or
abrasive finishing disks. The simultaneous action of the acid and abrasive
particles in the compound combines an abrasive and erosive action that has been
called the “abrosion effect.”10 This process removes the superficial
layer of enamel and simultaneously compacts some of the residual abraded
mineral byproduct into the enamel surface.10 The newly formed smooth,
dense mineralized layer at the enamel surface is approximately 15-μm thick6 and has a
glass-like texture and lustrous surface layer that has been designated the
“enamel glaze.”

Table. Clinical Protocol for Enamel Microabrasion

Evaluate the depth of discoloration and faciolingual
thickness of affected tooth;

Shoot preoperative photographs for documentation

Placement of dental dam

Initiate microreduction with fine-grit diamond bur

Application of microabrasion compound

Rotary application of compound, rinsing, and evaluation
of discoloration

Repeat applications until discoloration is removed or
discontinue and select another restorative option

Apply neutral sodium fluoride gel for 4 minutes

After
treatment, further superficial improvements may result from the continued
remineralization process in the oral cavity, while the new optical properties
of this mineralized layer have been shown to camouflage residual discoloration.10
In addition, tooth hydration from the saliva enhances the optical
properties of this altered enamel. This enamel microabrasion procedure, in
combination with fluoride treatment, may have the combined effect of inhibiting
demineralization.6 In vitro polarized light and scanning electron
microscopic studies have shown that this “enamel glaze” surface is more
resistant to demineralization and to colonization of Streptococcus mutans.1,10
Additional benefits of this procedure include its conservative nature, its
relative affordability for the patient, and the decrease in dental plaque
accumulation; remineralization and potential preventative dentistry
applications are also promoted.9,10

The
determinant for treatment with microabrasion depends upon the depth of the
enamel defect. The depth of discoloration can sometimes be determined by visual
inspection of the affected tooth from the incisal; however, the depth of some
defects can be elusive. The patient should thus be informed preoperatively that
if this procedure does not eliminate the discoloration and/or the facial
surface contour is altered to a flat or concave shape, an alternative procedure
can be performed.

A
combined therapy of microabrasion and composite bonding is one method that
should be considered for those enamel defects that are too deep for elimination
and for some dentinal discolorations (Figures 1-2-3-4). Prior to bonding,
however, it is imperative that the microabraded enamel surface be prepared with
a diamond bur and/or the etchant should be applied for 30 to 45 seconds longer
than the normal specified time, since the mineralized enamel glaze has a
tendency to resist the etchant.11

Conclusion

Chemical
biomodification of tooth discoloration is a treatment modality that encompasses
the three principle objectives of modern restorative dentistry: prevention,
preservation, and the perpetuation of longevity. This treatment philosophy
allows for a more conservative approach to aesthetic deficiencies that can often
be provided without sacrificing the patient’s tooth structure and the
clinician’s ethics.